Apparatus for providing ducts through casing in a well



1964 1.. CALDWELL 3, 20,

APPARATUS FOR PROVIDING DUCTS THROUGH CASING IN A WELL Filed Feb. 19, 1960 Cluznwsz. 1.,

zzvwszvrox United States Patent Ofilice Famed fgiifgiii 3,12%,268 AIPARATUS FOR PROVlDlNG DUCTS THROUGH CASENG IN A WELL Lyle Caldwell, Ethos Angeles, Calif., assignor to National Petroleum Corporah'on Limited, Caigary, Alberta,

Canada, a Canadian corporation Fiied Feb. 19, 1969, Ser. No. 9,959 7 Claims. (Cl. 1661 9) The present invention relates generally to oil wells, and more especially to devices for providing or forming fluid ducts behaveen oil bearing strata exposed in a well hole bore and the interior of casing or the like which has been lowered in the well bore and set in place, as by cementing.

It is well known in the art that, after a well is bored through the oil bearing strata, steel casing is lowered into the well to the vicinity of the oil bearing strata. Cement is then placed in the well outside of the cas'mg to sefl off the well bore above and below the strata from water or other foreign material. This is done in order to isolate dle production zone and permit only the desired oil to reach the interior of the casing. However, it is necessary to provide ducts which extend between the interior of the casing and the wall of the bore drilled through the oil bearing strata, such ducts extending necessarily through the casing and through the cement which surrounds the casing and fills the well bore outside of the casing.

There are various known methods of forming these ducts. Of known methods and apparatus, one type of apparatus of particular interest here is that disclosed in Patent No. 2,775,304 granted December 25, 1956, to Zandmer. This patent discloses telescoping members which are mounted on the casing prior to lowering it into the well bore and which can afterwards be extended to project beyond the casing a distance sufiiciently great to reach the wall of the well bore. After extending the telescoping members, the cement is placed and allowed to set; although it is also possible to extend the members after the cement is placed and while the cement is still soft and plastic. The telescoping members are generally protected by temporary wall members which prevent the cement from entering and filling the ducts, the wall members being removable chemically to open up the ducts and allow oil to reach the interior of the casing. Such devices are generally known as permeators in the industr and consequently will be so referred to here.

Known types of permeators have various shortcomings that restrict their use. One objection is that they are relatively expensive to make because of the plurality of individual parts involved, the gaskets to be fitted, and the care required in manufacture. The telescoping parts require careful machining to produce the close fits required to insure proper movement and at the same time to prevent leakage around them.

The designs of telescoping type permeators are such that they initially project a substantial distance beyond the outer surface of the casing. Since there are at least two and sometimes three telescoping members in a telescoping type permeator, the radial thicknesses of these members, one inside another, are additive and as a result the overall diameter of the completed permeator unit is such that it is sometimes necessary to mount the permeator emernally of a small diameter casing. These factors make it necessary that the bore hole be considerably larger than the outside diameter of the casing itself in order to receive a length of casing with permeators installed on it. The larger size of bore hole is more expensive to drill and to fill with cement so that it is advantageous to reduce the diameter of the bore hole to a minimum.

Another objection to known types of permeators is that the expansion raio is relatively limited. If there are two members in the unit, the ratio of the expanded permeator to the initial length of the same unit when retracted, is something less than 2: 1. This expansion ratio can be improved by having three members, two of which move relative to the stationary body, but even then an expansion ratio of less than 3:1 is the most possible. The maximum possible expansion ratio is obviously desirable since it permits the permeators to extend out from the wall of the casing for the greatest possible distance, again making practical the use of shorter, less expensive permeators.

It is accordingly a general object of my invention to provide a permeator of novel design that has a higher expansion ratio than heretofore possible.

It is also an object of my invention to provide a permeator of novel design that is smaller and has a shorter projection outside the casing for a given duct size than has been known heretofore.

It is a further object to provide a permeator of novel construction that is simple in construction, has fewer parts, and is relatively inexpensive to make.

These objects of my invention have been achieved in a permeator of my novel design by providing a body, having a central bore extending through it, that is adapted to be mounted in an opening through the casing wall, and a duct forming member mounted in the bore of said body, said duct forming member being of circular cross section and having a plurality of closely spaced annular folds or corrugations whereby the duct forming member may be extended axially by the application of internal fluid pressure which spreads the folds apart. A closure means is provided to close the outer end of the duct forming memher in order to hold within the member fluid under pressure and to receive the axial thrust of such fluid to extend the duct forming member. This closure member is made of a material that may be removed by a chemical reagent, for example, a material which is soluble in acid with relative ease. The duct forming members is preferably made of metal which is ductile and has little or no tendency to retract or shorten when the internal fluid pressure is reduced. Various materials and metals may obviously be used if they have the desired physical characteristics.

How the above and other objects and advantages of my invention are achieved will be better understood by reference to the following description, and to the annexed drawing, in which:

FIG. 1 is a fragmentary vertical section through the lower end of a bore hole and a casing set therein that is provided with duct forming members constructed according to my invention.

FIG. 2 is an enlarged fragmentary horizontal section through the casing and adjacent bore hole showing a permeator constructed according to my invention before it is expanded and the cement is in place.

FIG. 3 is a view similar to FIG. 2 showing the permeator expanded into contact with the wall of the bore hole and the cement in place.

FIG. 4 is an enlarged fragmentary longitudinal section through a variational form of a permeator illustrating details of construction.

Referring now to the drawing, and more especially to FIG. 1, there is shown a bore hole 10 which is drilled from the surface of the earth down into the ground to pass through the o l bearing strata 12. Inside the bore hole is the casing 14, which is ordinarily steel. The casing is of smaller diameter than the bore hole, there usually being an annular clearance of about one inch, more or less, between the outside of the casing and the wall of the bore hole. This annular space in the vicinity of the oil bearing strata is filled with a layer of cement 15, or other suitable material, which is bonded to the wall of the bore hole and to the casing in order to' provide a tight seal therewith.

The cement may be placed by any suitable method as far as the present invention is concerned. One method involves pumping the cement down casing 14 and out the open end to rise in the annular space around the casing. The cement is usually followed by a plug 17 which lodges in the casing at the bottom of the bore hole, such a plug separating the cement from the acid or other chemical solution used as described later.

A section of casing 14 opposite strata 12 is provided with a plurality of duct forming devices 16. These duct forming devices or permeators are shown in greater detail in FIGS. 2 and 3. Each permeator 16 has a 'body 20 consisting ofa shank 21 and an integral head 22.' The shank is preferably provided externally with screw threads in order that it may be threaded into an opening extending through the wall of casing 14. Head 22 is brought into contact with the exterior face of the casing and a sealing member may be provided at 23 in order to insure a fluid tight contact between the underside of head 22 and the outside surface of the casing. Head 22 may be provided with recesses 22a, or may be peripherally shaped, to receive a wrench by which the permeator body may be turned to screw it into the opening in the casing.

Each body 20 has an axially extending bore 24 which passes entirely through the body and it is in this bore that is located the duct forming member 25. This duct forming member is a tubular member which is normally circular viewed in cross section at any point along its length. However, viewed in longitudinal section as in FIG. 2 it will be seen to have a plurality of annular folds or corrugations which preferably are closely spaced. Although not so shown in the drawing, these folds are preferably brought into contact with one another in order'to reduce the initial length of the duct forming member 25 to a minimum. It will be recognized that in its construction the duct forming member 25 is similar to corrugated tubing, or to metallic bellows.

To the outer end of tubular member 25 is attached disc 26 which has a central opening that is closed by wall member 27. Disc 26 provides a suitable means for mounting wall member 27 on the outer end of the tube forming member in a manner to close the outer end of the latter member 25. Wall member 27 is tightly secured to washer 26, for reasons which will be further explained.

At the inner end, tubular member 25 is similarly provided with disc 28 which connects the inner end of the tubular member to body 29, this connection preferably being at the inner end of shank 21. Ordinarily it is preferred to close the central opening in disc 28 with wall member 36 which is tightly fitted to the washer to prevent'leakage around it and to resist'fiuid pressure.

The body 20 of each permeator is preferably made of steel because of its strength, ease of machining, and its ability to resist the chemical reagents that are used in a well. Discs 26 and 28 are similarly preferably made of steel. The duct forming member 25 may be made of a ferrous alloy but it may also be made from any one of a number of other metals, such as copper, aluminum, and their alloys. In general, any ductile metal which can be mechanically worked to produce the folds or corrugations in it and which can then be extended by the application of internal fluid pressure, is suitable for making the tube-forming members. However, the metal should also be one which is relatively inert with respect to the chemical reagents used.

The wall members 27 and 35) are removed, as will be explainedjby the application of suitable chemical reagents, normally acids. Consequently these two elements are made from a metal which will provide the necessary mechanical strength but which is dissolvable in .an' acid or other solution with relative ease. Alternatively the r 4 inner wall 30 may be a frangible member that can be ruptured by hydraulic pressure inside casing 14.

The method of using the permeators will. now be explained. The location of the oil bearing strata 12 in the bore hole having been determined by any suitable well surveying methods, which are not described here since they constitute no part of the present invention, the permeators 16 are located on the casing in positions so that they will be at the same levels as the oil bearing strata when the casing is lowered into the well. Thus the exact number and positions of the permeators are ordinarily determined by conditions existing in any indione in which the casing rests on the bottom of the bore hole, as shown in 1 16. 1, or is a short distance above the bottom. a

Cement is pumped down inside casing 14 and flows out the open bottom end, rising in the annular space around the casing to form the layer 15. The cement is followed after a suitable interval of. time by an acid solution which fills casing 14 for the depth of the casing to which permeators 16 are applied. To separate the acid from the element ahead of it, plug 17 is used; and the plug moves down inside the casing eventually coming to rest at or near the bottom. The purpose of this acid solution is to dissolve the inner wall members 30, thus opening members from the collapsed position of FIG. 2 to the' extended position of FIG. 3. When the wall 30 at the inner end of a permeator is dissolved or otherwise removed, the interior of the penneator is filled with fluid entering from the interior of casing 14. As pressure is applied to fluid in the casing, this pressure is transmitted to fluid in the permeator and exerts an axial thrust against the outer end wall 27. This axial thrust extends the tubular member 25 axially by expanding the folds or corrugations in the tubular member; The pressure at which the extension of the tube takes place can be closely regulated, since it is a function of the wall thickness of'the tubular member and the physical properties of the ma terial from which it is made. The permeators are typically. designed to expand only under a relatively high 1 unit internal pressure, perhaps 1080 psi. or more, in excess of the external or static pressure; but of course they may be designed to extend at a higher or. a lower unit pressure.

The time required to remove the inner walls 30 may be only a few minutes, after which only a short time is required to extend the permeators until they come into contact with the Wall of the bore hole, as shown in FIG. 3. Since this space is now filled with fluid or plastic cement, the operation of extending the permeators is accomplished before the cement hardens and while'it is still in a plastic state so that the permeators may push their way through this layer of material and reach the wall of the bore' wall once the permeator has ben extended into contact with the bore hole wall.

After the cement has set, the outer wall members 27 are subjected to a suitable chemical reagent, as for example acid, which dissolves them. This may be the same reagent used to remove walls 30 or a different one. When these walls are dissolved, the extended permeators provide a clear duct (as shown in FIG. 3) between the oil bearing strata and the interior of casing 14 through which fluids may be pumped into the oil strata and also through which oil and gas from the strata may flow in the reverse direction into the casing.

As an alternate procedure, the permeators may be expanded by hydraulic pressure prior to placing the cement; but it will be understood that the sequence of these various steps may be adapted to suit local conditions and is not limitative on my invention.

In the form of permeator described above, disc 26 is seated in an annular recess in head 22 but is not restrained or held in except by the duct member 25 or by friction. In FIG. 4 there is shown a variational construction in Which the body has a lip 2211 that is spun or turned over the margin of disc 26 to hold the disc in place. This insures that the permeators will not he accidentally extended by pressure changes. The lip is sheared off when the hydraulic pressure tending to extend the permeator exceeds a given value, or the end disc 26 may flex sufiiciently that it can slip past the lip. The circumferential length of lip 2% determines its shear strength and by controlling its total length, and thereby its shear strength, the pressure at which the permeator extends may be determined. Obviously a diametral shear pin or other similar arrangement may be substituted.

From the foregoing it will be seen that my improved permeator is simple in construction and operation. It eliminates any moving parts between which fluid-tight seals must be effected and maintained. Since there is only one member inside the body, the size of the body may be reduced more nearly to the external dimensions of the expansible tubular member and thus made much smaller than has heretofore been possible. Furthermore, it is possible by bringing the folds of the tubular member into contact with each other to produce one which can easily expand at least three times its original length, it having been demonstrated that expansion ratios as high as 5:1 are obtainable with the present construction.

It will be further evident from the foregoing description that various changes in the details of design and arrangement of the parts of the permeators may be made without departing from the spirit and scope of my invention. Accordingly it is to be understood that the foregoing description is considered as being illustrative of rather than limitative upon the invention as defined in the appended claims.

I claim:

1. Apparatus for providing a fluid duct through the wall of casing in a Well bore, comprising:

a body having a central bore extending through it and adapted to be mounted in an opening through the casing wall;

a duct forming member mounted in the bore of said body and attached thereto at the inner end of said member, said member being of circular cross section and having a plurality of closely spaced annular folds whereby the member is extensible axially by the application of fluid pressure within the member to space the folds farther apart, said duct forming member being capable at its inner end of receiving fluid from the casing;

and destructible ciosure means closing the outer end of the duct forming member to receive the axial thrust or" fluid under pressure in the duct forming member.

2. Apparatus as claimed in claim 1 in which the destructible closure means includes a member made of a material soluble in acid with relative ease while the duct forming member is made of a material that is substantially unaflected by the same acid.

3. Apparatus as claimed in claim 1 in which the radial dimension of the annular folds in the duct forming member is sufficient to render the duct forming member extensible to at least three times its initial length.

4. A permeator for casing adapted to be lowered into a bore hole comprising:

a body adapted to be mounted on the casing in an opening extending through the casing wall, and having a bore extending through the body;

an extensible, bellows-type duct forming member attached at its inner end to the body and adapted to be mounted in the bore in the body with its inner end exposed to the interior of the casing;

and destructible closure means closing the outer end of the duct forming member to receive a thrust axially of the duct forming member applied by fluid under pressure from the interior of the casing to elongate the duct forming member, said closure means being removable to provide a passage between the interior of the casing and the wall of the bore hole.

5. A permeator as in claim 4 in which the destructible closure means is or" a material soluble in a chemical solution with respect to which the material of the duct forming member is relatively insoluble.

6. A permeator as in claim 4 that also includes a second closure means at the inner end of the duct forming member closing the duct forming member to fluid from the casing interior, the second closure means being at least partly soluble in acid to open the duct forming member to fluid from the casing interior.

7. A permeator as in claim 4 in which the duct forming member is made of a ductile metal with substantially no tendency to shorten after once being elongated.

References Cited in the file of this patent UNITED STATES PATENTS 581,343 Frank Apr. 27, 1897 887,084 Fulton May 12, 1908 2,299,520 Yant Oct. 20, 1942 2,775,304 Zandmer Dec. 25, 1956 2,855,049 Zandmer Oct. 7, 1958 3,019,820 Yowell et al. Feb. 6, 1962 OTHER REFERENCES The Permeator: Pipeline to Greater Oil Recovery, The Oil and Gas Journal, vol. 57, No. 44, Oct. 26, 1959, pp. -105 incl. 

1. APPARATUS FOR PROVIDING A FLUID DUCT THROUGH THE WALL OF CASING IN A WELL BORE, COMPRISING: A BODY HAVING A CENTRAL BORE EXTENDING THROUGH IT AND ADAPTED TO BE MOUNTED IN AN OPENING THROUGH THE CASING WALL; A DUCT FORMING MEMBER MOUNTED IN THE BORE OF SAID BODY AND ATTACHED THERETO AT THE END OF SAID MEMBER, SAID MEMBER BEING OF CIRCULAR CROSS SECTION AND HAVING A PLURALITY OF CLOSELY SPACED ANNULAR FOLDS WHEREBY THE MEMBER IS EXTENSIBLE AXIALLY BY THE APPLICATION OF FLUID PRESSURE WITHIN THE MEMBER TO SPACE THE FOLDS FARTHER APART, SAID DUCT FORMING MEMBER BEING CAPABLE AT ITS INNER END OF RECEIVING FLUID FROM THE CASING; AND DESTRUCTIBLE CLOSURE MEANS CLOSING THE OUTER END OF THE DUCT FORMING MEMBER TO RECEIVE THE AXIAL THRUST OF FLUID UNDER PRESSURE IN THE DUCT FORMING MEMBER. 